The forming of you hands to look like hand guns, followed closely by the ridiculous movement of your hands back and forth to repeatedly point at someone. This will normally be done at the end of a bad joke and performed by someone who lacks social skills pointing to the person who they failed at making fun of.

Stephen- Nice slippers
Aaron- Their Moccasins
Stephen- Oh, well i'll just have to 'mock' you more then. <does da guns while speaking>
Aaron- <stares down stephen>
Stephen- <quietly walks away in shame>